Well, in any science “proven” is pretty strong language. I’d rather say that much of this has been more or less strongly corroborated under certain conditions, to a degree where we have some confidence that we’re not just pulling stuff out of our butts.
And in some other universe, I look like Brad Pitt, can play the guitar like Santana, and actually have a positive k/d ratio in online shooters.
It’s just fun scifi shit to talk about.
I’ll take this opportunity to shill for Scott Aaronson’s blog again: https://scottaaronson.blog/
Scott Aaronson is a theoretical computer science guy who is one of the world’s leading experts on quantum computation, and his blog covers progress in the field quite well, sometimes in semi-understandable form. He has a book that explains quantum computing to the layman: http://www.amazon.com/Quantum-Computing-since-Democritus-Aaronson/dp/0521199565 and he’s also posted on the blog his lecture notes for the introductory course.
First off, I’ll give a big second to Scott Aaronson’s blog that @antlers just posted.
Second, this:
The multiverse/many worlds interpretation is just that–an interpretation–and when it gets trotted out I always roll my eyes a bit because it’s (1) unprovable and (2) just makes the layperson think that QM is weird and totally out of touch. Which it kind of is, but not to the extent that the multiverse would make you think.
Finally, on the topic at hand (IBM’s 127 qubit processor), it’s a super impressive achievement, but lets remember that these are physical qubits. That is, they are not fault-tolerant logical qubits. Things like factoring (and therefore breaking encryption) require thousands of logical qubits, and with current* error rates you need something like a million physical qubits to make one logical qubit. So we’re not near anything like that any time soon.
What IBM’s computer probably can do is some kind of toy problem (that is at least somewhat fault-tolerant) that a top-of-the-line datacenter can’t do, but that isn’t actually useful for anything.
*current = a couple years out of date, and it is a fast moving field, so it’s probably less than that.
FTL communication is still theoretically impossible. The idea is that you have, say, two electron spins created in such a way that they’re in opposite directions. But quantum weirdness means neither spin is determined until you measure it, just that they’re opposite. But you can separate them by any distance and then as soon as you measure the spin of one, the whole system decoheres and the spin of the other is determined. This has been shown to occur faster than the speed of light. There’s no way to use this scheme for communication because you still have to transmit information about the state of the system via a classical channel. But it does violate Bell’s inequality and leads to some weirdness about non-local phenomena that might violate causality (or more probably would make us think of locality differently.)
Virtual particles are a mathematical abstraction that permit physicists to find solutions to the path integral formulation of quantum field theory. It’s not clear if they’re real in the sense that they actually “exist” or if the possibility of their existence perturbs the probability waves in QFT. (“Real” particles themselves are just local excitations of a quantum field.)
The double slit experiment for single photons (or electrons) fired one at a time exhibits an interference pattern if we don’t try to measure which slit the particle passes through, suggesting it propagates through both slits like a wave front. But if we do try to determine which slit it passes through, it definitely passes through one or the other and instead of an interference pattern, we see a single bright spot behind both slits. The particle is definitely always a wave. Everything is waves. There is no wave-particle duality; that is an answered question. But when we conduct a measurement on the wave, it seems to force it into a local peak and the wide spread of probabilities that the wave initially represented collapses into a very narrow range that looks like the localized packet of mass/energy we call a particle. The act of measurement somehow affects the wave.
So a quantum computer could hypothetically do the Stable Marriage problem for everyone on earth?
Brad Pitt and Santana I’ll give you… but that last one seems unpossible. ;)
In my layman’s imagination point / wave duality gets rid of infinities - imagine a radiating wave inside something like a perfect Dyson Sphere. If it touches all sides of the sphere simultaneously then it would have more energy than it emitted. Or something like that. ^^. Collapsing down to a point preserves something about its energy state.
Virtual particles do have some reality right? Casimir forces?
Entanglement just seems to be implying something about two particles being actually the same particle. I feel like surely that has some insight into quantum reality, but I’m not equipped to make such insights.
Describing quantum computing as a “speed up because you do the calculations in multiple universes at once” is one of Aaronson’s pet peeves. The real advantage is that while a classical bit represents one of two values, a single qubit represents a complex-valued probability distribution (think of a complex number with magnitude 1 as a circle on the complex plane; a qubit is a set of probabilities for every point around the circle). Combining qubits in quantum gates produces resulting qubits that reflect the input’s probability distributions in ways that are predictable but computationally intensive for a classical computer to simulate. The difficulty in simulation grows exponentially with number of quantum operations, because a qubit in general can’t be “simplified”; while you will start a computation by preparing qubits in simple states, the probability distribution represented by a qubit later in a computation will reflect all the operations leading up to it. For certain specialized problems, combining qubits in the right ways will produce useful results that are computationally infeasible with classical computers.
The abitlity to surpass the capabilities of classical computers has already been demonstrated for a class of problems that are “natural” for a quantum computer to do: Boson Sampling, which essentially simulates the behavior of a photon passing through a collection of quantum gates. But Boson Sampling requires a relatively small number of quantum operations compared to those required for the real game-changing computations. To use Shor’s Algorithm to factor thousand-bit integers with a quantum computer would require many thousands of quantum gate operations to be performed reliably, and existing quantum computing operations get overwhelmed by noise long before they get there. There are proposed error-correction algorithms that seem to put such computations in reach, but even error correction requires a minimum level of reliability that hasn’t been reach yet.
I confess I don’t follow this.
I’m not a quantum physicist. I only know what I saw on PBS SpaceTime :)
Yeah, I mean I gather it’s more that they comprise one system that evolves as a whole.
The “wavefront” of a wave radiating in all directions can be described as the surface of a sphere. As the radius doubles the surface area of the sphere increases by 4x. If the wave contacts another spherical surface that it’s inside of, if the waveform didn’t collapse it would have more energy at the point of contact than it did when it was emitted. If it didn’t collapse it would need to change frequency as the inverse to its emission radius squared like the forces do
“Naked” forces have always worried me. I feel there’s something there about them, but I can’t really know more than that.
But as the radius doubles, the amplitude of a spherical wave decreases by 4x also, so that the total energy is constant.
It’s quantum physics’ version of rolling the bones. 127 sounds like a lot of bones, so it’s better.
Oh you’re right, thanks for clarifying that! In my head i was mixing up linear waves, which don’t change amplitude, and using that logic in spherical propagation. This is why casual physics is always bad physics.
What happens when this thread hits “127” replies? Do we enter an alternate dimensional universe?
Sweet summer child. We are already in an alternate dimensional universe. Have the last five years taught you nothing? :)
Yes, that’s the one I’m desperately trying to escape. This version of Idiocracy sucks!
I see your point. But what if tampering makes it worse?
